Polymer film and laminate

Abstract

The present invention aims to provide a polymer thin film and a laminate with low dielectric loss tangent and a small difference in the coefficient of linear expansion with that of copper foil. The polymer thin film of the present invention comprises a liquid crystal polymer, wherein, in a cross-section cut along the thickness direction of the polymer thin film, the hardness A at a distance of half the thickness of the polymer thin film and the hardness B at a distance of 1 / 10 the thickness of the polymer thin film satisfy the relationship of Equation (1A). When the distances of 1 / 10, 4 / 10, and 6 / 10 of the thickness of the polymer thin film are respectively designated as positions T1, T2, and T3, and the distance from one surface to position T1 is designated as the first surface region, and the distance from position T2 to position T3 is designated as the central region, the void area ratio X in the first surface region and the void area ratio Y in the central region satisfy the relationship of Equation (2A). Equation (1A): (Hardness A + Hardness B) / 2 ≥ 0.10 GPa Equation (2A): Void area ratio Y - Void area ratio X ≥ 0.10%

Description

Technical Field

[0001] This invention relates to a polymer film and a laminate. Prior Technology

[0002] The 5G mobile communication system, known as the next generation of communication technology, uses higher frequency bands than before. Therefore, from the perspective of reducing transmission loss in high frequency bands, the thin film substrates used in circuit boards for 5G mobile communication systems require low dielectric loss tangent and low water absorption, and development based on various raw materials is underway.

[0003] For example, Patent Document 1 describes a thermoplastic liquid crystal polymer film and a laminate having a film layer and a metal layer composed of a thermoplastic liquid crystal polymer film. The thermoplastic liquid crystal polymer film is a liquid crystal polymer film composed of a thermoplastic polymer that can form an optically anisotropic molten phase, and the rate of change of the relative permittivity before and after heating the film satisfies a specific relationship.

[0004] [Patent Document 1] Japanese Patent No. 6640072 Summary of the Invention

[0005] As mentioned above, polymer films with low dielectric loss tangent are required. The hardness of the polymer film is related to the dielectric loss tangent; therefore, polymer films with high hardness are sometimes used to achieve a low dielectric loss tangent. However, when hot-pressing high-hardness polymer films and copper foils to manufacture laminates, warping or peeling of the polymer film from the copper foil sometimes occurs in the resulting laminate. One method to solve this problem is to use a polymer film with a smaller difference in coefficient of linear expansion compared to the copper foil. The inventors, based on their evaluation of the polymer film as described in Patent Document 1, have determined that although it has a low dielectric loss tangent, the difference between its coefficient of linear expansion and that of the copper foil is large, and there is room for improvement.

[0006] Therefore, the objective of this invention is to provide a polymer film with low dielectric loss tangent and a small difference in coefficient of linear expansion with that of copper foil. Furthermore, the objective of this invention is to provide a laminate having the above-described polymer film and a metal layer.

[0007] As a result of in-depth research conducted by the inventors to solve the above-mentioned problems, they discovered that in polymer films, as long as the hardness at a specific location in the thickness direction meets a predetermined relationship, and the proportion of void area in a specific region in the thickness direction meets a predetermined relationship, the dielectric loss tangent becomes lower, and the difference between the dielectric loss tangent and the linear expansion coefficient of copper foil becomes smaller, thus completing the present invention. That is, the inventors have found that the above-mentioned problems can be solved by the following configuration.

[0008] [1] A polymer film comprising a liquid crystal polymer, In a cross-section taken along the thickness direction of the polymer film, when the hardness at position A, located at half the thickness of the polymer film from one surface to another, is defined as hardness A, and the hardness at position B, located at 1 / 10 the thickness of the polymer film from one surface to another, is defined as hardness B, the following relationship (1A) is satisfied. In the above cross-section, when moving from one surface of the polymer film toward the other surface, the position located at 1 / 10 of the thickness of the polymer film is designated as position T1, the position located at 4 / 10 of the thickness of the polymer film is designated as position T2, the position located at 6 / 10 of the thickness of the polymer film is designated as position T3, the area from one surface to position T1 is designated as the first surface region, the area from position T2 to position T3 is designated as the central region, the area ratio of the voids in the first surface region is designated as the void area ratio X, and the area ratio of the voids in the central region is designated as the void area ratio Y, the following relationship (2A) is satisfied. Formula (1A) (hardness A + hardness B) / 2 ≥ 0.10 GPa Equation (2A) Void area ratio Y - Void area ratio X ≥ 0.10% [2] The polymer film as described in [1], wherein the hardness A and the hardness B satisfy the following relationship (1B). Formula (1B) (Hardness A - Hardness B) ≥ -0.02 GPa [3] The polymer film described in [1] or [2] is a single-layer structure. [4] The polymer film as described in any one of [1] to [3], wherein the dielectric loss tangent of the polymer film at a temperature of 23°C and a frequency of 28GHz is less than 0.0024. [5] The polymer film as described in any one of [1] to [4], wherein the liquid crystal polymer comprises at least one selected from the group consisting of repeating units derived from p-hydroxybenzoic acid and repeating units derived from 6-hydroxy-2-naphthoic acid. [6] A laminate having a polymer film as described in any one of [1] to [5] and at least one metal layer. [7] The laminate as described in [6] has at least two metal-containing layers, wherein the metal-containing layers, the polymer film and the metal-containing layers are sequentially arranged. [8] The laminate as described in [6] or [7], wherein the thickness of the metal layer is 5 to 30 μm. [Invention Effects]

[0009] According to the present invention, a polymer film with low dielectric loss tangent and a small difference in the coefficient of linear expansion with that of copper foil, and a laminate containing the polymer film can be provided. Simple Explanation of the Diagram

[0010] Figure 1 is a cross-sectional view showing an example of the configuration of a manufacturing apparatus for producing polymer films based on blow molding. Implementation

[0011] The present invention will now be described in detail. The description of the constituent elements set forth below is sometimes based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

[0012] In this specification, when the polymer film or laminate is elongated, the length direction refers to the long side direction and the MD (machine direction) direction of the polymer film or laminate, and the width direction refers to the direction perpendicular to the length direction (short side direction and TD (transverse direction)) within the surface of the polymer film or laminate. In this specification, each component may be represented by a single equivalent substance, or by two or more substances. When two or more substances are used for each component, the content of each component, unless otherwise specified, refers to the total content of the two or more substances. In this specification, "~" is used to include the values ​​recorded before and after it as lower and upper limits. In this specification, the dielectric loss tangent of a polymer film or a liquid crystal polymer contained in a polymer film, measured at a temperature of 23°C and a frequency of 28 GHz, is recorded as the "standard dielectric loss tangent".

[0013] [Polymer Film] The polymer film of the present invention comprises a liquid crystal polymer. Furthermore, when the hardness at position A, which is located at half the thickness of the polymer film from one surface toward another surface, is defined as hardness A, and the hardness at position B, which is located at 1 / 10 the thickness of the polymer film from one surface toward the other surface, is defined as hardness B, the following relationship (1A) is satisfied. Furthermore, in the above cross-section, when moving from one surface of the polymer film toward the other surface, the position located at 1 / 10 of the thickness of the polymer film is designated as position T1, the position located at 4 / 10 of the thickness of the polymer film is designated as position T2, the position located at 6 / 10 of the thickness of the polymer film is designated as position T3, the area from one surface to position T1 is designated as the first surface region, the area from position T2 to position T3 is designated as the central region, the area ratio of the voids in the first surface region is designated as the void area ratio X, and the area ratio of the voids in the central region is designated as the void area ratio Y, the following relationship (2A) is satisfied. Formula (1A) (hardness A + hardness B) / 2 ≥ 0.10 GPa Equation (2A) Void area ratio Y - Void area ratio X ≥ 0.10%

[0014] The polymer film of the present invention has a low dielectric loss tangent and a small difference in coefficient of linear expansion with that of copper foil. The details of the reason for this are not yet clear, but are presumed to be roughly as follows. Polymer films with high hardness tend to exhibit low standard dielectric loss tangent. Here, the above formula (1A) represents the relationship between the hardness in the center of the polymer film thickness and the hardness in the surface layer. Polymer films that satisfy formula (1A) can be said to have high overall film hardness, and therefore it is presumed that they exhibit low standard dielectric loss tangent.

[0015] In the case of using polymer films in the manufacture of circuit boards, they can be used in the form of a laminate consisting of a polymer film and copper foil. In this case, if the polymer film has high hardness, it can cause warping of the laminate when heated, or reduce the adhesion between the polymer film and the copper foil. One method for solving this problem is to minimize the difference in the coefficients of linear expansion between the polymer film and the copper foil. The inventors have discovered that by using a polymer film that satisfies both formula (1A) and formula (2A), the difference in the coefficients of linear expansion between the polymer film and the copper foil can be reduced. Equation (2A) above represents the relationship between the proportion of void area in the surface portion of the polymer film and the proportion of void area in the center portion of the polymer film's thickness. The rationale is not yet clear, but it is believed that polymer films with void area ratios satisfying Equation (2A) have their elongation controlled in the thickness direction and their expansion in the in-plane direction suppressed. As a result, even when using a high-hardness polymer film such as one satisfying Equation (1A), Equation (2A) is still satisfied, thus it is speculated that the difference between the coefficient of linear expansion and that of copper foil is unexpectedly smaller.

[0016] 〔hardness〕 Regarding the polymer film of the present invention, in a cross-section cut along the thickness direction of the polymer film, when the hardness at position A, which is located at half the thickness of the polymer film from one surface to another, is set as hardness A, and the hardness at position B, which is located at 1 / 10 the thickness of the polymer film from one surface to another, is set as hardness B, the following relationship (1A) is satisfied. Formula (1A) (hardness A + hardness B) / 2 ≥ 0.10 GPa

[0017] From the viewpoint of achieving better results in this invention, it is preferable that the lower limit of "(hardness A + hardness B) / 2" in formula (1A) is 0.12 GPa or higher, more preferably 0.14 GPa or higher, and even more preferably 0.16 GPa or higher. From the viewpoint of achieving better results in this invention, it is preferable that the upper limit of “(hardness A + hardness B) / 2” in formula (1A) is 0.30 GPa or less, more preferably 0.25 GPa or less, and even more preferably 0.20 GPa or less.

[0018] From the viewpoint of achieving better results in this invention, it is preferable that hardness A and hardness B further satisfy the relationship of equation (1B). Formula (1B) (Hardness A - Hardness B) ≥ -0.02 GPa

[0019] From the viewpoint of achieving better results in this invention, it is preferable that the lower limit of "(hardness A - hardness B)" in formula (1B) is -0.01 GPa or higher, and even more preferable that it is 0.00 GPa or higher. From the viewpoint of achieving better results in this invention, it is preferable that the upper limit of "(hardness A - hardness B)" in formula (1B) is 0.06 GPa or less, more preferably 0.04 GPa or less, and even more preferably 0.02 GPa or less.

[0020] From the viewpoint of achieving better results with the present invention, a hardness A of 0.10~0.25GPa is preferred, and 0.12~0.20GPa is even more preferred. From the viewpoint of achieving better results with the present invention, a hardness B of 0.12~0.30 GPa is preferred, and 0.14~0.25 GPa is even more preferred.

[0021] The hardness of the polymer film in cross-section is the indentation hardness measured using a nano-indenter according to ISO 14577, and the specific measurement method is described in the examples below. Furthermore, the value of "(hardness A + hardness B) / 2" in the polymer film can be adjusted, for example, by performing the specific heat treatment described later in the polymer film forming process and controlling the heat (temperature × time) in the annealing process described later. Furthermore, the value of "(hardness A - hardness B)" in the polymer film can be adjusted, for example, by performing the specific heat treatment described later in the polymer film forming process, and by controlling the heat in the thickness direction of the polymer film during the annealing process described later.

[0022] [Void area ratio] Regarding the polymer film of the present invention, in a cross-section cut along the thickness direction of the polymer film, when moving from one surface of the polymer film to another surface, the position located at 1 / 10 of the thickness of the polymer film is designated as position T1, the position located at 4 / 10 of the thickness of the polymer film is designated as position T2, the position located at 6 / 10 of the thickness of the polymer film is designated as position T3, the area from one surface to the aforementioned position T1 is designated as the first surface region, the area from position T2 to position T3 is designated as the central region, the area ratio of the voids in the first surface region is designated as the void area ratio X, and the area ratio of the voids in the central region is designated as the void area ratio Y, the following relationship (2A) is satisfied. Equation (2A) Void area ratio Y - Void area ratio X ≥ 0.10%

[0023] From the viewpoint of achieving better results in this invention, it is preferable that the lower limit of "void area ratio Y - void area ratio X" in formula (2A) is 0.20% or more, and even more preferable that it is 0.30% or more. From the viewpoint of achieving better results in this invention, it is preferable that the upper limit of "void area ratio Y - void area ratio X" in formula (2A) is 0.70% or less, more preferably 0.60% or less, and even more preferably 0.50% or less.

[0024] From the viewpoint of achieving better results with the present invention, a void area ratio X of 8-20% is preferred, and 10-18% is even better. From the viewpoint of achieving better results with the present invention, a void area ratio Y of 10-22% is preferred, and 12-20% is even better.

[0025] The porosity ratio of each region in the cross-section of the polymer film refers to the ratio (%) of the area of ​​the porosity in each region to the area of ​​each region in the cross-section of the polymer film. Regarding the porosity ratio, after immersing the polymer film, cut to expose its thickness direction, in propylamine, the cross-section of the polymer film is photographed using a scanning electron microscope (SEM). The ratio is determined based on data obtained by image processing software (ImageJ). The specific measurement method is described in the examples described later. Furthermore, the values ​​of the void area ratio (void area ratio X and Y) and "void area ratio Y - void area ratio X" in the polymer film can be adjusted, for example, by performing the specific heat treatment described later in the polymer film forming process, controlling the heat (temperature × time) in the annealing process described later, and controlling the heat applied to the thickness direction of the polymer film in the annealing process described later.

[0026] 〔Element〕 The following is a detailed description of the components contained in the polymer film.

[0027] <Liquid Crystal Polymer> The liquid crystal polymer contained in the polymer film of the present invention is not particularly limited, for example, a melt-formable liquid crystal polymer can be cited. Thermotropic liquid crystal polymers are preferred as liquid crystal polymers. Thermotropic liquid crystal polymers refer to polymers that exhibit liquid crystal properties in a molten state when heated within a predetermined temperature range. As long as the thermotropic liquid crystal polymer is a liquid crystal polymer that can be melt-molded, its chemical composition is not particularly restricted. For example, thermoplastic liquid crystal polyester and thermoplastic polyester amide with amide bonds introduced into the thermoplastic liquid crystal polyester can be cited. As a liquid crystal polymer, for example, the thermoplastic liquid crystal polymer described in International Patent Application Publication No. 2015 / 064437 and Japanese Patent Application Publication No. 2019-116586 can be used.

[0028] More specifically, examples of liquid crystal polymers include thermoplastic liquid crystal polyesters or thermoplastic liquid crystal polyester amides having repeating units selected from the group consisting of at least one of aromatic hydroxycarboxylic acids, aromatic or aliphatic diols, aromatic or aliphatic dicarboxylic acids, aromatic diamines, aromatic hydroxyamines and aromatic aminocarboxylic acids.

[0029] Examples of aromatic hydroxycarboxylic acids include p-hydroxybenzoic acid, m-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and 4-(4-hydroxyphenyl)benzoic acid. These compounds may have substituents such as halogen atoms, lower alkyl groups, and phenyl groups. Among these, p-hydroxybenzoic acid or 6-hydroxy-2-naphthoic acid is preferred. As an aromatic or aliphatic diol, an aromatic diol is preferred. Examples of aromatic diols include hydroquinone, 4,4'-dihydroxybiphenyl, 3,3'-dimethyl-1,1'-biphenyl-4,4'-diol and their acetylated derivatives, with hydroquinone or 4,4'-dihydroxybiphenyl being preferred. As an aromatic or aliphatic dicarboxylic acid, an aromatic dicarboxylic acid is preferred. Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, with terephthalic acid being preferred. Examples of aromatic diamines, aromatic hydroxyamines, and aromatic aminocarboxylic acids include p-phenylenediamine, 4-aminophenol, and 4-aminobenzoic acid.

[0030] Furthermore, it is preferable that the liquid crystal polymer has at least one selected from the group consisting of repeating units represented by formulas (1) to (3) below. -O-Ar1-CO-(1) -CO-Ar2-CO-(2) -X-Ar3-Y-(3) In formula (1), Ar1 represents phenyl, naphthyl or biphenyl. In formula (2), Ar2 represents a group represented by a phenyl group, a naphthyl group, a biphenyl group, or the group represented by formula (4) below. In formula (3), Ar3 represents a group represented by a phenyl group, a naphthyl group, a biphenyl group or the group represented by formula (4) below, and X and Y represent an oxygen atom or an imine group, respectively. -Ar4-Z-Ar5-(4) In formula (4), Ar4 and Ar5 independently represent phenyl or naphthyl groups, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonylutriate group, or an alkyl group. The aforementioned phenyl, naphthyl, and biphenyl groups may also have substituents selected from the group consisting of halogen atoms, alkyl groups, and aryl groups.

[0031] The liquid crystal polymer preferably has at least one of the following groups: repeating units of aromatic hydroxycarboxylic acids represented by formula (1) above, repeating units of aromatic diols represented by formula (3) above where X and Y are both oxygen atoms, and repeating units of aromatic dicarboxylic acids represented by formula (2) above. Furthermore, it is more preferable that the liquid crystal polymer has at least one repeating unit derived from an aromatic hydroxycarboxylic acid, and it is even more preferable that it has at least one repeating unit selected from the group including repeating units derived from p-hydroxybenzoic acid and repeating units derived from 6-hydroxy-2-naphthoic acid, and it is particularly preferable that it has repeating units derived from p-hydroxybenzoic acid and repeating units derived from 6-hydroxy-2-naphthoic acid.

[0032] Furthermore, as another preferred embodiment, from the viewpoint of further enhancing the effects of the present invention, it is more preferable that the liquid crystal polymer has at least one repeating unit selected from the group consisting of repeating units from 6-hydroxy-2-naphthoic acid, repeating units from aromatic diols, repeating units from terephthalic acid, and repeating units from 2,6-naphthalenedicarboxylic acid; it is further preferable that it has all repeating units from 6-hydroxy-2-naphthoic acid, repeating units from aromatic diols, repeating units from terephthalic acid, and repeating units from 2,6-naphthalenedicarboxylic acid.

[0033] When the liquid crystal polymer contains repeating units derived from aromatic hydroxycarboxylic acids, the composition ratio relative to all repeating units of the liquid crystal polymer is preferably 50-65 mol%. Furthermore, it is also preferable that the liquid crystal polymer contains only repeating units derived from aromatic hydroxycarboxylic acids. When the liquid crystal polymer contains repeating units derived from aromatic diols, the composition ratio relative to all repeating units of the liquid crystal polymer is preferably 17.5 to 25 mol%. When the liquid crystal polymer contains repeating units derived from aromatic dicarboxylic acids, the composition ratio relative to all repeating units of the liquid crystal polymer is preferably 11 to 23 mol%. When the liquid crystal polymer contains repeating units derived from any one of aromatic diamines, aromatic hydroxyamines, and aromatic aminocarboxylic acids, the composition ratio relative to all repeating units of the liquid crystal polymer is preferably 2 to 8 mol%.

[0034] The synthesis method of liquid crystal polymers is not particularly limited, and the above compounds can be synthesized by known methods such as melt polymerization, solid-state polymerization, solution polymerization and slurry polymerization. Commercially available products can also be used as liquid crystal polymers. Examples of commercially available liquid crystal polymers include "Laperos" manufactured by Polyplastics Co., Ltd., "Vectra" manufactured by Celanese Corporation, "UENO LCP" manufactured by UENO FINE CHEMICALS INDUSTRY, LTD., "Sumika Super LCP" manufactured by Sumitomo Chemical Co., Ltd., "Zider" manufactured by ENEOS Corporation, and "Siveras" manufactured by Toray Industries, Inc. Furthermore, liquid crystal polymers can form chemical bonds within polymer films with crosslinking agents or compatibility components (reactive compatibilizers), which can be any type of component. This also applies to components other than liquid crystal polymers.

[0035] From the viewpoint of easily manufacturing polymer films with low standard dielectric loss tangent (preferably below 0.0025), a standard dielectric loss tangent of 0.0022 or less is preferred for liquid crystal polymers, below 0.0015 is more preferred, and below 0.0010 is even more preferred. The lower limit value is not particularly limited, for example, it can be above 0.0001. Furthermore, when the polymer film contains two or more liquid crystal polymers, "the dielectric loss tangent of the liquid crystal polymer" refers to the average mass of the dielectric loss tangents of the two or more liquid crystal polymers.

[0036] The standard dielectric loss tangent of the liquid crystal polymer contained in the polymer film can be measured by the following method. First, the polymer film is impregnated in an organic solvent (e.g., pentafluorophenol) at a mass ratio of 1000 times the total mass of the polymer film. Then, it is heated at 120°C for 12 hours to leach the solvent-soluble components containing the liquid crystal polymer into the solvent. Next, the leachate containing the liquid crystal polymer is separated from the non-leachable components by filtration. Then, acetone, a poor solvent, is added to the leachate to precipitate the liquid crystal polymer, and the precipitate is separated by filtration. The obtained precipitate was filled into a PTFE (polytetrafluoroethylene) tubing (outer diameter 2.5 mm, inner diameter 1.5 mm, length 10 mm). The dielectric properties were measured using a cavity resonator (e.g., KANTO Electronic Application and Development Inc. "CP-531") at a temperature of 23°C and a frequency of 28 GHz. The influence of voids in the PTFE tubing was corrected using the Bruggeman formula and porosity, thereby obtaining the standard dielectric loss tangent of the liquid crystal polymer. The porosity (volume fraction of voids within the hose) is calculated as follows. The volume of the space within the hose is determined using the hose's inner diameter and length. Next, the weight of the hose before and after filling with the precipitate is measured to determine the mass of the filled precipitate. The volume of the filled precipitate is then calculated by dividing this mass by the precipitate's specific gravity. The filling ratio is then calculated by dividing this precipitate volume by the volume of the space within the hose, thereby determining the porosity. Furthermore, when using commercially available products made of liquid crystal polymers, the dielectric loss tangent value recorded in the catalog of such products can also be used.

[0037] From the perspective of superior heat resistance, a melting point Tm of 250°C or higher is preferred for liquid crystal polymers, 280°C or higher is even better, and 310°C or higher is even more preferred. The upper limit of the melting point Tm of liquid crystal polymers is not particularly limited, but from the point of view of better moldability, below 400°C is better, and below 380°C is even better. The melting point Tm of a liquid crystal polymer can be determined by measuring the temperature at which the endothermic peak appears using a differential scanning calorimeter (DSC-60A, manufactured by Shimadzu Corporation). When using commercially available liquid crystal polymers, the melting point Tm value listed in their catalog can also be used.

[0038] There are no particular limitations on the number average molecular weight (Mn) of the liquid crystal polymer, but 10,000 to 600,000 is preferred, and 30,000 to 150,000 is even better. The number-average molecular weight of the liquid crystal polymer is a conversion value based on standard polystyrene using gel permeation chromatography (GPC). GPC measurements can be performed under the following equipment and conditions. The measuring apparatus used was a TOSOH CORPORATION "HLC (registered trademark)-8320GPC" column, and the column consisted of two TSKgel (registered trademark) SuperHM-H (6.0 mm ID × 15 cm, TOSOH CORPORATION). The solvent (elution buffer) for dissolving the liquid crystal polymer was not particularly limited, but a mixture of pentafluorophenol and chloroform in a 1 / 2 (mass ratio) solution could be used as an example. The measurement conditions were set as follows: sample concentration 0.03% by mass, flow rate 0.6 ml / min, sample injection volume 20 μL, and measurement temperature 40 °C. Detection was performed using a RI (differential refractive index) detector. The calibration curves were prepared using eight samples from TOSOH CORPORATION: "TSK standard, polystyrene", "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000" and "n-propylbenzene".

[0039] The polymer film may contain one liquid crystal polymer or two or more liquid crystal polymers. The content of liquid crystal polymer relative to the total mass of the polymer film is preferably 40~99.9% by mass, more preferably 50~95% by mass, and further preferably 60~90% by mass. Furthermore, the content of liquid crystal polymer and the components described later in the polymer film can be measured by known methods such as infrared spectroscopy and gas chromatography-mass spectrometry.

[0040] <Any ingredient> The polymer film may contain any components other than the polymers described above. Examples of such components include polyolefins, compatibility components, heat stabilizers, and additives described later.

[0041] (Polyolefins) Polymer films may contain polyolefins. In this specification, "polyolefin" refers to a polymer (polyolefin resin) having repeating units derived from olefins. Polymer films containing liquid crystal polymers and polyolefins are preferred, while those containing liquid crystal polymers, polyolefins, and compatible components are even better.

[0042] Polyolefins can be linear or branched. Furthermore, polycyclic olefins, for example, can have a cyclic structure. Examples of polyolefins include polyethylene, polypropylene (PP), polymethylpentene (TPX manufactured by Mitsui Chemicals, Inc.), hydrogenated polybutadiene, cyclic olefin polymers (COP, Zeonoa manufactured by Zeon Corporation, etc.) and cyclic olefin copolymers (COC, Apel manufactured by Mitsui Chemicals, Inc., etc.). Polyethylene can be either high-density polyethylene (HDPE) or low-density polyethylene (LDPE). Furthermore, polyethylene can be linear low-density polyethylene (LLDPE).

[0043] Polyolefins can be copolymers of olefins with monomers other than olefins, such as acrylates, methacrylates, styrene and / or vinyl acetate. Examples of polyolefins that can be used as copolymers include styrene-ethylene / butene-styrene copolymers (SEBS). SEBS can be hydrogenated. From the viewpoint of achieving better results, it is preferable to have a smaller copolymerization ratio of copolymerizing components other than olefins, and even more preferable to have no copolymerizing components present. For example, it is preferable that the content of the copolymerizing components is 0 to 40% by mass relative to the total mass of the polyolefin, and even more preferable that it is 0 to 5% by mass. Furthermore, it is preferable that the polyolefin does not substantially contain the reactive groups described later, and it is preferable that the content of repeating units with reactive groups is 0 to 3% by mass relative to the total mass of the polyolefin.

[0044] As polyolefins, polyethylene, COP, or COC are preferred, with polyethylene being even better, and low-density polyethylene (LDPE) being even better.

[0045] Polyolefins can be used alone or in combination with two or more types. When the polymer film contains polyolefin, from the viewpoint of superior surface properties, it is preferable that the content is 0.1% by mass or more relative to the total mass of the polymer film, and more preferably 5% by mass or more. There is no particular upper limit, but from the viewpoint of superior smoothness of the polymer film, it is preferable that the content is 50% by mass or less relative to the total mass of the polymer film, more preferably 40% by mass or less, and further preferably 25% by mass or less. Furthermore, when the polyolefin content is 50% by mass or less, it is easier to sufficiently increase the heat distortion temperature and to achieve good weld heat resistance.

[0046] (compatible ingredients) Examples of compatibility components include polymers having a portion that is highly compatible with or has a high affinity for liquid crystal polymers (non-reactive compatibilizers) and polymers having reactive groups that have phenolic hydroxyl or carboxyl groups at the ends of liquid crystal polymers (reactive compatibilizers). For reactive compatibilizers, epoxy groups or maleic anhydride groups are preferred. As a compatibility component, copolymers with a high degree of compatibility or affinity for polyolefins are preferred. Furthermore, when the polymer film contains both polyolefins and a compatibility component, a reactive compatibility agent is preferred, considering that the polyolefin can be micro-dispersed as the compatibility component. Furthermore, compatible components (especially reactive compatibilizers) in polymer films can form components and chemical bonds with liquid crystal polymers, etc.

[0047] Examples of reactive compatibilizers include epoxy-containing polyolefin copolymers, epoxy-containing ethylene copolymers, maleic anhydride-containing polyolefin copolymers, maleic anhydride-containing vinyl copolymers, oxazoline-containing polyolefin copolymers, oxazoline-containing ethylene copolymers, and carboxyl-containing olefin copolymers. Among these, epoxy-containing polyolefin copolymers or maleic anhydride-grafted polyolefin copolymers are preferred.

[0048] Examples of epoxy-containing polyolefin copolymers include ethylene / epoxypropylene methacrylate copolymers, ethylene / epoxypropylene methacrylate / vinyl acetate copolymers, ethylene / epoxypropylene methacrylate / methyl acrylate copolymers, polystyrene graft copolymers of ethylene / epoxypropylene methacrylate copolymers (EGMA-g-PS), polymethyl methacrylate graft copolymers of ethylene / epoxypropylene methacrylate copolymers (EGMA-g-PMMA), and acrylonitrile / styrene graft copolymers of ethylene / epoxypropylene methacrylate copolymers (EGMA-g-AS). Commercially available epoxy-containing polyolefin copolymers include, for example, Bond First 2C and BONDFAST E manufactured by Sumitomo Chemical Co., Ltd.; Lotadar manufactured by ARKEMA KK; and Modiper A4100 and Modiper A4400 manufactured by NOF CORPORATION.

[0049] Examples of epoxy-containing ethylene copolymers include propylene methacrylate-grafted polystyrene (PS-g-GMA), propylene methacrylate-grafted polymethyl methacrylate (PMMA-g-GMA), and propylene methacrylate-grafted polyacrylonitrile (PAN-g-GMA).

[0050] Examples of polyolefin copolymers containing maleic anhydride include maleic anhydride-grafted polypropylene (PP-g-MAH), maleic anhydride-grafted ethylene / propylene rubber (EPR-g-MAH), and maleic anhydride-grafted ethylene / propylene / diene rubber (EPDM-g-MAH). Commercially available products containing maleic anhydride polyolefin copolymers include, for example, the Orevac G series manufactured by ARKEMA KK and the FUSABOND E series manufactured by Dow Chemical Company.

[0051] Examples of vinyl copolymers containing maleic anhydride include maleic anhydride-grafted polystyrene (PS-g-MAH), maleic anhydride-grafted styrene / butadiene / styrene copolymer (SBS-g-MAH), maleic anhydride-grafted styrene / ethylene / butene / styrene copolymer (SEBS-g-MAH), styrene / maleic anhydride copolymer, and acrylate / maleic anhydride copolymer. As a commercially available product containing maleic anhydride vinyl copolymers, the Tuftec M series (SEBS-g-MAH) manufactured by Asahi Kasei Corporation is an example.

[0052] In addition to the above, compatibilizers that can be cited as compatibilizers include oxazoline-based compatibilizers (e.g., bisoxazoline-maleic anhydride-modified polyethylene and bisoxazoline-maleic anhydride-modified polypropylene), elastic system compatibilizers (e.g., aromatic resins and petroleum resins), ethylene methacrylate epoxy propylene copolymer, ethylene maleic anhydride ethyl acrylate copolymer, ethylene methacrylate epoxy propylene-acrylonitrile styrene, acid-modified polyethylene paraffin, COOH-modified polyethylene graft polymer, COOH-modified polypropylene graft polymer, polyethylene-polyamide graft copolymer, polypropylene-polyamide graft copolymer, methyl methacrylate-butadiene-styrene copolymer, acrylonitrile-butadiene rubber, EVA-PVC graft copolymer, vinyl acetate-ethylene copolymer, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, hydrogenated styrene-isopropylene-block copolymer, and amine-modified styrene-ethylene-butene-styrene copolymer.

[0053] Furthermore, ionomer resins can be used as a compatible component. Examples of such ionomer resins include ethylene-methacrylic acid copolymer ionomers, ethylene-acrylic acid copolymer ionomers, propylene-methacrylic acid copolymer ionomers, propylene-acrylic acid copolymer ionomers, butene-acrylic acid copolymer ionomers, ethylene-vinyl sulfonic acid copolymer ionomers, styrene-methacrylic acid copolymer ionomers, sulfonated polystyrene ionomers, fluorinated ionomers, telechelated polybutadiene-acrylic acid ionomers, sulfonated ethylene-propylene-diene copolymer ionomers, hydrogenated polypentamer ionomers, polypentamer ionomers, poly(vinylpyridinium salt) ionomers, poly(vinyltrimethylammonium salt) ionomers, poly(vinylbenzylphosphonium salt) ionomers, styrene-butadiene-acrylic acid copolymer ionomers, polyurethane ionomers, sulfonated styrene-2-acrylamide-2-methylpropane sulfate ionomers, acid-amine ionomers, aliphatic ionomers, and aromatic ionomers.

[0054] When the polymer film contains compatible components, it is preferable that the content of the components relative to the total mass of the polymer film is 0.05 to 30% by mass, more preferably 0.1 to 20% by mass, and even more preferably 0.5 to 10% by mass.

[0055] -Heat stabilizer- To suppress thermal oxidative degradation during melt extrusion film formation and improve the planarity and smoothness of the polymer film surface, the polymer film may contain a heat stabilizer. Examples of heat stabilizers include: phenolic and amine stabilizers with free radical scavenging properties; phosphite stabilizers and sulfur stabilizers with peroxide decomposition properties; and mixed stabilizers with both free radical scavenging and peroxide decomposition properties.

[0056] Examples of phenolic stabilizers include hindered phenolic stabilizers, semi-hindered phenolic stabilizers, and low-hindered phenolic stabilizers. Commercially available low-hindered phenolic stabilizers include, for example, ADEKASTAB AO-20, AO-50, AO-60 and AO-330 manufactured by ADEKA CORPORATION; and Irganox 259, 1035 and 1098 manufactured by BASF. Commercially available semi-hindered phenolic stabilizers include, for example, ADEKASTAB AO-80 manufactured by ADEKA CORPORATION and Irganox 245 manufactured by BASF. Commercially available low-hindered phenolic stabilizers include, for example, Nocrack 300 manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO.,LTD.; and ADEKASTAB AO-30 and AO-40 manufactured by ADEKA CORPORATION. Commercially available phosphite stabilizers include, for example, ADEKASTAB 2112, PEP-8, PEP-36, and HP-10 manufactured by ADEKA CORPORATION. Commercially available products that are mixed stabilizers include, for example, SUMILIZER GP manufactured by Sumitomo Chemical Company, Limited.

[0057] From the perspective of superior heat stabilization effect, hindered phenolic stabilizers, semi-hindered phenolic stabilizers, or phosphite stabilizers are preferred, with hindered phenolic stabilizers being even better. On the other hand, from the perspective of electrical properties, semi-hindered phenolic stabilizers or phosphite stabilizers are even better.

[0058] A heat stabilizer can be used alone or in combination with two or more. When the polymer film contains a heat stabilizer, the content of the heat stabilizer relative to the total mass of the polymer film is preferably 0.0001 to 10% by mass, more preferably 0.01 to 5% by mass, and even more preferably 0.1 to 2% by mass.

[0059] (additive) Polymer films may contain additives in addition to the components mentioned above. Examples of additives include plasticizers, lubricants, inorganic and organic particles, and UV-absorbing materials.

[0060] Examples of plasticizers include alkyl phthaloglycolic acid alkyl esters, bisphenol compounds (bisphenol A, bisphenol F), phosphate esters, carboxylic acid esters, and polyols. The content of the plasticizer relative to the total mass of the polymer film can be 0-5% by mass. Examples of lubricants include fatty acid esters and metal soaps (such as inorganic stearic acid salts). The lubricant content relative to the total mass of the polymer film can be 0 to 5% by mass. The polymer film may contain reinforcing materials, matting agents, dielectric constant modifiers, or inorganic and / or organic particles. Examples of inorganic particles include silicon dioxide, titanium dioxide, barium sulfate, talc, zirconium dioxide, alumina, silicon nitride, silicon carbide, calcium carbonate, silicates, glass beads, graphite, tungsten carbide, carbon black, clay, mica, carbon fiber, glass fiber, and metal powder. Examples of organic particles include cross-linked acrylic acid and cross-linked styrene. The content of inorganic and organic particles relative to the total mass of the polymer film can be 0 to 50% by mass. Examples of UV-absorbing materials include salicylate compounds, benzophenone compounds, benzotriazole compounds, substituted acrylonitrile compounds, and triazine compounds. The content of the UV-absorbing material relative to the total mass of the polymer film can be 0 to 5% by mass.

[0061] Furthermore, polymer films can contain polymer components other than liquid crystal polymers. Examples of the aforementioned polymer components include thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, and polyester ether ketone.

[0062] <Properties of Polymer Films> (thickness) The thickness of the polymer film is preferably 5~1000μm, more preferably 10~500μm, and even more preferably 20~300μm. Furthermore, the thickness of the polymer film is obtained by observing the cross-section along the thickness direction of the laminate using a scanning electron microscope (SEM), and measuring the thickness of the polymer film at any 100 different points, which is the arithmetic mean of the measured values.

[0063] (Dielectric properties) The standard dielectric loss tangent of the polymer film is not particularly limited, but is preferably below 0.0025, below 0.0024, even better below 0.0022, further better below 0.0020, particularly good below 0.0015, and best below 0.0010. The lower limit is not particularly limited and can be above 0.0001. The relative permittivity of polymer films varies depending on their application, but 2.0 to 4.0 is preferred, and 2.5 to 3.5 is even better. The dielectric properties of polymer films, including the standard dielectric loss tangent and relative permittivity, can be measured using the cavity resonator perturbation method. Specific methods for measuring the dielectric properties of polymer films are described in the Examples section below.

[0064] (Coefficient of linear expansion) The in-plane coefficient of linear expansion (CTE) of the polymer film is preferably 14~22 ppm / ℃, more preferably 16~20 ppm / ℃, and even more preferably 17~19 ppm / ℃. If the in-plane linear expansion coefficient of the polymer film is within the above range, the difference between it and the linear expansion coefficient of the copper foil (18ppm / ℃) is small. Therefore, it can suppress the warping of the laminate containing the copper foil and the polymer film during manufacturing, and also ensure good adhesion between the copper foil and the polymer film. The in-plane linear expansion coefficient of the polymer film can be set within the above range, for example, by using a polymer film that satisfies the above formula (2A). The method for measuring the in-plane linear expansion coefficient of polymer films is described in the examples described later.

[0065] Polymer films can be single-layer structures or multi-layer structures composed of multiple layers. Furthermore, a "single-layer structure" polymer film means that the polymer film is composed of a single material throughout its overall thickness.

[0066] [Methods for manufacturing polymer films] As for the manufacturing method of polymer films, there is no particular limitation as long as it is a method that can manufacture polymer films that satisfy formula (1A) and formula (2A), but it is better to manufacture polymer films by blow molding. More specifically, the manufacturing method of the polymer film includes a granulation process in which the components constituting the polymer film are mixed to obtain particles, and a film forming process in which the polymer film is formed by blow molding using the molten resin formed from the particles. Examples of methods include performing specific heat treatment and annealing treatments as described later in the film forming process. The following is a detailed description of the process for fabricating polymer films containing liquid crystal polymers.

[0067] <Granulation Process> (1) Raw material form Polymers such as liquid crystal polymers used in film forming can also be used directly in granular, flake, or powder form. However, for the purpose of film stabilization or uniform dispersion of additives (referring to components other than liquid crystal polymers, hereinafter the same), granules can be obtained by mixing one or more raw materials (referring to at least one of polymers and additives, hereinafter the same) using an extruder and then granulating them.

[0068] (2) Drying or using vents as a substitute for drying. It is preferable to dry the liquid crystal polymer and additives before granulation. Drying methods include circulating heated air with a low dew point and dehumidifying by vacuum drying. In particular, vacuum drying or drying using inert gases is preferable for resins that are easily oxidized.

[0069] (3) Raw material supply method The raw material supply method can be a method of pre-mixing raw materials before compounding and granulation, a method of supplying raw materials separately so that they are in a certain proportion in the extruder, or a method of combining the two.

[0070] (4) Atmosphere during extrusion During melt extrusion, it is best to prevent thermal and oxidative degradation as much as possible without hindering uniform dispersion. Using a vacuum pump to reduce pressure or introducing inert gas to lower the oxygen concentration is also effective. These methods can be implemented individually or in combination.

[0071] (5) Temperature It is preferable to set the mixing temperature below the thermal decomposition temperature of the liquid crystal polymer and additives. It is also preferable to set it to a low temperature as much as possible, within the range where the load on the extruder and the decrease in uniform mixing are not a problem.

[0072] (6) Pressure It is preferable to carry out the compounding resin pressure during granulation at 0.05~30MPa. When the resin is prone to coloring or gelation due to shearing, it is preferable to apply an internal pressure of about 1~10MPa in the extruder to fill the twin-shaft extruder with resin raw material.

[0073] (7) Granulation method As a pelletizing method, the material extruded in noodle form is generally solidified in water and then cut. However, it can also be granulated by underwater cutting, which involves melting the material in an extruder and then cutting it while extruding it directly in water with a die, or by thermal cutting, which involves cutting the material in a hot state.

[0074] (8) Particle size The preferred particle size is a cross-sectional area of ​​1~300mm² and a length of 1~30mm, while a cross-sectional area of ​​2~100mm² and a length of 1.5~10mm is even better.

[0075] (dry) (1) Drying purpose It is preferable to reduce the moisture and volatile components in the particles before melt film formation, and drying the particles is effective. When the particles contain moisture or volatile components, it can sometimes cause not only air bubbles to be incorporated into the polymer film or a deterioration in appearance due to a decrease in haze, but also a decrease in physical properties due to the cleavage of the liquid crystal polymer molecular chains or roller contamination due to the formation of monomers or oligomers. Furthermore, depending on the type of liquid crystal polymer used, drying to remove dissolved oxygen can sometimes suppress the formation of oxidative crosslinks during melt film formation.

[0076] (2) Drying method and heating method Regarding drying methods, from the perspective of drying efficiency and economy, dehumidifying hot air dryers are generally used; however, there are no particular restrictions as long as the target moisture content can be obtained. Furthermore, selecting a more suitable method based on the physical properties of the liquid crystal polymer is also acceptable. Examples of heating methods include pressurized steam, heater heating, far-infrared irradiation, microwave heating, and heat medium circulation heating.

[0077] <Membrane Fabrication Process> The following describes a process for forming a polymer film using particles containing liquid crystal polymers via blow molding.

[0078] (Extrusion conditions) Raw material drying In the melt plasticizing process of extruded granules, it is better to reduce moisture and volatile components, just like in the granulation process, and drying the granules is effective.

[0079] Raw material supply method When multiple types of raw materials (granules) are fed into the extruder, they can be pre-mixed (premixing method), fed separately to achieve a certain proportion within the extruder, or a combination of both. Furthermore, to stabilize the extrusion process, it is generally desirable to minimize variations in the temperature and volumetric density of the raw materials fed into the extruder. From the perspective of plasticization efficiency, a higher raw material temperature is preferable, provided it does not adhere to the feed port. Specifically, for amorphous resins, a temperature range of {glass transition temperature (Tg) (°C) - 150°C} to {Tg (°C) - 1°C} is preferred, and for crystalline resins, a range of {melting point (Tm) (°C) - 150°C} to {Tm (°C) - 1°C} is preferred, and the raw materials should be heated or kept at a specific temperature. Also, from the perspective of plasticization efficiency, a volumetric density of the raw material that is at least 0.3 times that of the molten state is preferred, and more preferably at least 0.4 times. When the volumetric specific gravity of the raw material is less than 0.3 times that of the molten state, it is better to carry out processing such as granulation by compressing the raw material.

[0080] The atmosphere during extrusion Similar to the granulation process, the atmosphere during melt extrusion needs to minimize thermal and oxidative degradation without hindering uniform dispersion. Injecting inert gases (such as nitrogen), using a vacuum funnel to reduce the oxygen concentration within the extruder, and installing vents on the extruder for vacuum pump-based pressure reduction are all effective methods. These pressure reductions and inert gas injections can be implemented independently or in combination.

[0081] • Rotational speed The extruder rotation speed is preferably 5-300 rpm, more preferably 10-200 rpm, and further preferably 15-100 rpm. If the rotation speed is above the lower limit, the residence time is shortened, which can suppress the decrease in molecular weight caused by thermal degradation and also suppress discoloration. If the rotation speed is below the upper limit, it can suppress the cleavage of molecular chains caused by shearing and suppress the decrease in molecular weight and the increase in cross-linked gel. Regarding the rotation speed, considering both uniform dispersion and thermal degradation caused by prolonged residence time, selecting suitable conditions is preferable.

[0082] ·temperature The barrel temperatures (feed section temperature T1℃, compression section temperature T2℃, and measuring section temperature T3℃) are generally determined using the following method. When the extruder is used to melt and plasticize the granules at the target temperature T℃, the measuring section temperature T3 is set to T±20℃, taking into account the heat of shear. At this time, T2 is set considering the extrusion stability and the thermal decomposition of the resin within the range of T3±20℃. T1 is generally set to {T2(℃)-5℃}~{T2(℃)-150℃}, taking into account both ensuring friction between the resin and the barrel, which serves as the driving force (feed force) for resin transport, and preheating in the feed section, to select the optimal value. In the case of a typical extruder, the temperatures can be set by subdividing the T1~T3 zones, and by setting the temperature to be more stable with smoother temperature changes between each zone, further stabilization can be achieved. At this point, it is preferable to set T below the resin's thermal degradation temperature. When the thermal degradation temperature is exceeded due to shear heating from the extruder, active cooling is generally employed to remove the shear heating. Furthermore, in order to balance improved dispersibility and thermal degradation, it is also effective to use a higher temperature for melt mixing in the first half of the extruder and lower the resin temperature in the second half.

[0083] ·pressure The resin pressure inside the extruder is typically 1–50 MPa. From the perspective of extrusion stability and melt uniformity, 2–30 MPa is preferable, and 3–20 MPa is even better. If the pressure inside the extruder is above 1 MPa, the insufficient melt filling rate within the extruder can suppress extrusion pressure instability and the formation of foreign matter caused by stagnant areas. Furthermore, if the pressure inside the extruder is below 50 MPa, excessive shear stress within the extruder can be suppressed, thus preventing thermal decomposition caused by rising resin temperature.

[0084] ·stay time The residence time in the extruder (residence time during film formation) is calculated, similarly to that in the granulation process, from the volume of the extruder section and the polymer discharge capacity. A residence time of 10 seconds to 60 minutes is preferred, 15 seconds to 45 minutes is more preferred, and 30 seconds to 30 minutes is further preferred. If the residence time is 10 seconds or more, melt plasticization and additive dispersion become sufficient. If the residence time is less than 30 minutes, it is preferable to suppress resin deterioration and discoloration.

[0085] (filter) • Types, Purpose of Setup, Structure To prevent damage to the gear pump caused by foreign matter contained in the raw materials and to extend the life of the micro-pore filter installed downstream of the extruder, filtration equipment is generally installed at the extruder outlet. A combination of mesh filter media and reinforcing plates with high strength and open area is preferred, known as a circuit breaker plate filter.

[0086] Mesh size and filtration area A mesh size of 40-800 mesh is preferred, 60-700 mesh is even better, and 100-600 mesh is further preferred. A mesh size of 40 mesh or larger can effectively suppress the passage of foreign matter. Furthermore, a mesh size of 800 mesh or smaller can suppress the rate of increase in filtration pressure and reduce the mesh exchange frequency. From the perspective of filtration accuracy and maintenance strength, filter meshes often employ a combination of multiple mesh sizes. Also, because this increases the filtration opening area and maintains mesh strength, a breaker plate is sometimes used to reinforce the filter mesh. From the perspective of filtration efficiency and strength, the opening ratio of the breaker plate used is typically 30-80%. Furthermore, filter replacement devices mostly use the same diameter as the extruder barrel, but to increase the filtration area, sometimes conical piping is used, along with larger diameter filter meshes or branched flow paths using multiple circuit breaker plates. The filtration area is preferably selected based on a flow rate of 0.05~5 g / cm², more preferably 0.1~3 g / cm², and further preferably 0.2~2 g / cm². The filter pressure increases due to filter blockage caused by the capture of foreign objects. In this case, it is necessary to stop the extruder and replace the filter, but it is also possible to use a type that allows filter replacement while extrusion continues. Furthermore, as a countermeasure against the increase in filter pressure caused by the capture of foreign objects, it is also possible to use a device that has the function of washing away and removing the foreign objects captured by the filter by reversing the flow path of the polymer, thereby reducing the filter pressure.

[0087] (Blow bag forming) Hereinafter, while illustrating a specific manufacturing apparatus, an example of an embodiment of the manufacturing method for manufacturing the polymer film of the present invention by blow molding will be described. The method for manufacturing the polymer film of the present invention is not limited to the following embodiments. From the viewpoint that it is easy to manufacture the polymer film that satisfies the above-described formulas (1A) and (2A), it is preferable to manufacture the polymer film by the method of this embodiment.

[0088] Figure 1 is a cross-sectional view showing an example of the configuration of a manufacturing apparatus for producing polymer films based on blow molding. The film-forming apparatus 10 shown in Figure 1 includes: an annular mold 12 with an annular slit, a cooling blower 14, a heater 16, and a cooler 18. In the film-forming apparatus 10, the annular mold 12, the cooling blower 14, the heater 16, and the cooler 18 are arranged sequentially from the vertically lower side. Furthermore, the film-forming apparatus 10 is configured to supply gas to the internal space of the molten cylindrical film F extruded from the annular mold 12.

[0089] Molten liquid crystal polymer is continuously supplied to an annular die 12 via an extruder (not shown). The supplied molten liquid crystal polymer is extruded into a cylindrical film F through the annular slit of the annular die 12 and extended vertically. The extruded cylindrical film F expands in diameter due to the air supplied to its interior, and is simultaneously cooled and solidified in the frosting line FL by a cooling airflow ejected from a cooling blower 14 arranged concentrically above and with the annular die 12. Heater 16 and cooler 18 are used for specific heat treatments described later.

[0090] Regarding the temperature of the molten material ejected from the annular mold 12 (the temperature at the outlet of the supply mechanism), from the viewpoint of improving the formability of the liquid crystal polymer and suppressing its degradation, the melting point of the liquid crystal polymer is preferably set to Tm (°C), with {Tm-10} to {Tm+40}°C. As an indicator of melt viscosity, 50 to 3500 Pa·s is preferred.

[0091] The elongation ratio of the cylindrical film F in the blown bag forming film-making process of this embodiment is not particularly limited. The ratio (Br / Dr) of the elongation ratio in the TD direction (blow ratio: Br) to the elongation ratio in the MD direction (elongation ratio: Dr) is preferably 1.5 to 5, and more preferably 2.0 to 4.5. Furthermore, the elongation ratio (Dr) in the MD direction is preferably 1.0 to 5 times, 1.1 to 3 times, and even better 1.2 to 2 times. Also, the elongation ratio (Br) in the TD direction is preferably 1.5 to 20 times, 2 to 15 times, and even better 2.5 to 14 times.

[0092] (Specific heat treatment) In the manufacturing method of this embodiment, during the expansion process by blow molding, the following heat treatment process is performed: before curing the cylindrical film F, the cylindrical film F is reheated using heater 16, and then the cylindrical film F is cooled using cooler 18. Hereinafter, the series of heat treatments including reheating and cooling performed during the expansion process of the cylindrical film F will be described as "specific heat treatment". Before curing (before reaching the frost line FL), the expanded cylindrical film F is subjected to a specific heat treatment, thereby easily generating a thickness-direction hardness distribution in the cylindrical film F, where the hardness is higher in the center of the thickness direction and lower in the surface layer near the surface, but the overall hardness of the film is considered to be higher. Although this hardness distribution is easily generated and the detailed mechanism of the increased hardness of the film as a whole is not yet clear, the inventors speculate that the film surface is heated to a temperature near the melting point by reheating treatment, and then the film surface is immediately cooled after heating in a way that hinders blown film formation, thereby changing the crystalline structure of the surface layer of the film by melting and rapid cooling.

[0093] Regarding the timing of specific heat treatment, there are no particular restrictions as long as it is performed before the curing of the cylindrical film. It is preferable to perform the heat treatment after the elongation ratio of the cylindrical film F in the expansion process exceeds 50%, more preferably after it exceeds 80%, and even more preferably after it exceeds 90%, relative to the final elongation ratio in the TD direction based on the blow molding. The elongation ratio in the TD direction can be confirmed by measuring the diameter or circumferential length of the cylindrical film F. Furthermore, the timing for reheating the cylindrical film F is adjusted by adjusting the vertical position of the heater 16. The same applies to the position of the cooler 18 and the timing for cooling.

[0094] The conditions for a specific heat treatment are adjusted appropriately based on the materials constituting the polymer film and the intended hardness. Regarding the reheating temperature, considering the need for a clearer understanding of the hardness distribution along the thickness direction, the melting point of the liquid crystal polymer is set as Tm (°C), preferably above {Tm-10}°C, and even better above Tm. Furthermore, considering the need to suppress thickness inhomogeneity caused by film softening, a reheating temperature below {Tm+20}°C is preferred, and even better below {Tm+15}°C. The reheating time varies depending on the heating mechanism and the heating temperature, but 0.2 to 15 seconds is preferred, and 1 to 10 seconds is even better. As for the heating mechanism (heater 16) used for reheating, known heating mechanisms such as hot air dryers and infrared heaters can be cited. Since infrared heaters can increase the surface temperature of the film in a short time, they are preferred. Furthermore, it is preferable to reduce the temperature difference in the circumferential direction of the cylindrical film F by arranging the heating mechanism around the cylindrical film F for reheating.

[0095] Regarding the cooling process in a specific heat treatment, it is preferable to perform it rapidly after reheating in order to suppress the formation of structural defects and uneven thickness in the surface layer of the film. Regarding the cooling process, it is preferable to cool the surface temperature of the cylindrical film F at a rate of -10°C / second or higher (more preferably -20°C / second or higher, and even more preferably -30°C / second or higher). It is preferable that the cooling process continues until the surface temperature of the cylindrical film F is below the aforementioned crystallization temperature. The crystallization temperature is measured at the recrystallization peak temperature when heated to above the melting point by DSC and cooled at a rate of 10°C / min. The specific cooling time varies depending on the cooling mechanism and the temperature of the film surface heated by reheating, but 0.3 to 15 seconds is preferable, and 2 to 5 seconds is even better. As a cooling mechanism (cooler 18) for cooling treatment, known cooling devices can be used, but it is preferable to use a blower that blows air (preferably cold air) onto the cylindrical film F. It is preferable to place such a blower around the cylindrical film F to perform cooling so that the temperature difference in the circumferential direction is reduced.

[0096] Above the film-forming apparatus 10, the cured cylindrical film F is held by rollers (not shown) and then wound by a winding machine (not shown) to obtain a polymer film.

[0097] • Mitigation In this embodiment, the following mitigation process can be performed: strain present within the polymer film is mitigated by heat-shrinking and blow-forming the polymer film. During the mitigation process, the polymer film is heat-shrinked in the TD direction under tension (e.g., approximately 2.0~3.0 kg / mm² in the MD direction). A shrinkage rate of 1% or more, preferably 1.5% or more, is preferred in the TD direction. The upper limit of the shrinkage rate can be appropriately determined based on the film, but it is generally below 4% in the TD direction. The easing treatment can be carried out, for example, by introducing the polymer film into a known heating device such as a hot air drying oven. Regarding the set temperature for the easing treatment, the melting point of the liquid crystal polymer is set as Tm (°C), with temperatures below Tm being preferred, and below {Tm-30}°C being even more preferred. The lower limit is not particularly limited, but temperatures above {Tm-120}°C are preferred, and above {Tm-90}°C are even more preferred. Alternatively, a set temperature of approximately 200-290°C is preferred, and approximately 230-270°C is even more preferred.

[0098] (Annealing treatment) In the manufacturing method of this embodiment, after a specific heat treatment, an annealing process is performed, heating the polymer film to near its melting temperature. It is preferable that the annealing process is performed after the specific heat treatment and before the tempering treatment.

[0099] By annealing after a specific heat treatment (preferably a mild treatment), the molecular weight of the liquid crystal domains in the polymer film increases.

[0100] By setting the melting point of the polymer film as Tm (°C), it is easy to obtain a polymer film that satisfies the above formula (2A). From this perspective, the heating temperature during annealing is preferably {Tm-30}°C to {Tm+10}°C, and even more preferably {Tm-25}°C to {Tm+5}°C. The heating time during annealing is preferably 10 seconds to 24 hours, and even more preferably 4 to 12 hours. Examples of heating mechanisms used in annealing processes include hot air drying ovens and hot presses (e.g., dough presses or heated rollers), with hot presses being preferred. From the perspective of suppressing the deformation of polymer films during heating, it is preferable to use a composite material formed by laminating a polymer film onto an adhesive (e.g., a metal foil such as copper foil or aluminum foil) in the annealing process. When annealing a composite, it is preferable to perform heat treatment to make the coefficient of thermal expansion of the polymer film the same as that of the adhesive (e.g., 16×10⁻⁶ to 26×10⁻⁶ cm / cm / ℃) before annealing. After annealing the composite, the adhesive is peeled off from the composite to obtain the polymer film.

[0101] After annealing, a further heat easing treatment can be performed.

[0102] Surface Treatment Surface treatment of polymer films is preferred as it can further improve the adhesion between the polymer film and metal or other layers. Examples of surface treatments include glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, and acid or alkali treatment. The glow discharge treatment mentioned here can be a low-temperature plasma generated under a low-pressure gas of 10⁻³ to 20 Torr; plasma treatment at atmospheric pressure is also preferred. Glow discharge processing is performed using plasma-excited gases. A plasma-excited gas system refers to gases that are excited by plasma under the conditions described above; examples include fluorochloroalkyl groups such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, and tetrafluoromethane, as well as mixtures thereof.

[0103] To improve the mechanical properties, thermal dimensional stability, or curl shape of the rolled polymer film, it is also useful to cure the polymer film at a temperature below the Tg of the liquid crystal polymer. Furthermore, after the film-forming process, the polymer film can be further subjected to a process of clamping the polymer film with heated rollers and / or a stretching process to further improve the smoothness of the polymer film.

[0104] [Laminated body] The laminate of the present invention has the above-described polymer film and at least one metal layer. The structure of the laminate of the present invention will be described in detail below.

[0105] The laminate has at least one metal layer and at least one polymer film. There is no limit to the number of metal layers and polymer films in the laminate; each layer may be only one or more. The laminate can be a single-area laminate with only one metal layer on one side of a single polymer film, or a two-area laminate with two metal layers on both sides of a single polymer film. Preferably, the laminate has at least one layer consisting of a metal layer, a polymer film, and a metal layer stacked in sequence.

[0106] Furthermore, the laminate can have a multilayer structure with alternating layers of three or more metal layers and two or more polymer thin films. That is, the laminate can have a multilayer structure with three or more metal layers or metal wiring disposed via an insulating layer composed of polymer thin films. Laminates with such multilayer structures can be used as highly functionalized multilayer circuit boards (e.g., 2-layer circuit boards, 3-layer circuit boards, and 4-layer circuit boards). The multilayer assembly can be a single-layer circuit board having two metal layers or metal wiring and one insulating layer made of polymer film. Alternatively, the multilayer assembly can be an intermediate having one or two metal layers or metal wiring and one insulating layer made of polymer film, and used to manufacture a multilayer assembly having the above-mentioned multilayer structure.

[0107] [Including a metal layer] Regarding metal-containing layers, there are no particular restrictions on the type of metal-containing layer as long as it is formed on the surface of the polymer film. Examples include metal layers that completely cover the surface of the polymer film and metal wiring formed on the surface of the polymer film. Materials constituting the metal layer include, for example, metals used for electrical connections. Examples of such metals include copper, gold, silver, nickel, aluminum, and alloys containing any of these metals. Examples of alloys include copper-zinc alloys, copper-nickel alloys, and zinc-nickel alloys. From the perspective of excellent conductivity and processability, copper is the preferred material for constituting the metal layer. Copper layers or copper wiring composed of copper or copper alloys containing 95% or more copper by mass are preferred as metal layers. Examples of copper layers include rolled copper foil manufactured by rolling and electrolytic copper foil manufactured by electrolysis. Chemical treatments such as pickling can be applied to the metal layer.

[0108] As will be described later, the metal layer is made using, for example, metal foil, and the wiring pattern is formed as needed using known processing methods. When using metal foil such as copper foil in the fabrication of the laminate, from the viewpoint of achieving better results in this invention, it is preferable that the surface roughness Ra of the metal foil surface (at least one surface) is 3 μm or less, and more preferably 1.5 μm or less. The lower limit is not particularly limited; for example, 0.1 μm or more, and 0.3 μm or more are preferred. Metal foils with a surface roughness Ra within the aforementioned range, such as unroughened copper foil, are commercially available. The Ra of the metal foil and the surface containing the metal layer is determined using a surface roughness measuring instrument (e.g., Mitutoyo Corporation, product name: SURFTEST SJ-201) by a method based on JIS B 0601. Specific measurement methods are described in the examples described later.

[0109] The thickness of the metal layer is not particularly limited and can be appropriately selected according to the application of the circuit board. However, from the perspective of wiring conductivity and economy, 1~100μm is better, 5~30μm is even better, and 10~20μm is even better.

[0110] The laminate may have layers other than polymer films and metal layers, depending on the requirements. Examples of other layers include adhesive layers, rust-preventive layers, and heat-resistant layers.

[0111] <Next layer> From the perspective of superior adhesion between polymer films and metal-containing layers, it is preferable for laminates to have an adhesive layer. When the laminate has an adhesive layer, it is preferable that the adhesive layer is disposed between the polymer film and the metal-containing layer. For example, when two metal-containing layers are disposed on both sides of the polymer film, it is preferable to laminate in the following order: metal-containing layer, adhesive layer, polymer film, adhesive layer, and metal-containing layer.

[0112] As an adhesive layer, known adhesive layers used in the manufacture of wiring boards such as copper-clad laminates can be used, such as a layer composed of a hardened material containing an adhesive composition of a known adhesive resin. The adhesive composition used to form the adhesive layer is not particularly limited. For example, a composition containing an adhesive resin can be included as an arbitrary component, and further includes at least one selected from the group consisting of reactive compounds and additives described below.

[0113] (Adhesive resin) Examples of adhesive resins include (meth)acrylic acid resins, polyvinyl cinnamate, polycarbonate, polyimide, polyamide-imide, polyesterimide, polyetherimide, polyetherketone, polyetheretherketone, polyether sulfide, polysulfide, parylene, polyester, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, polyurethane, polyvinyl alcohol, cellulose ester, fluorinated resins, liquid crystal polymers, syndiotactic polystyrene, silicone resins, epoxy silicone resins, phenolic resins, alkyd resins, epoxy resins, maleic acid resins, melamine resins, urea resins, aromatic sulfonamides, benzoguanamine resins, silicone elastomers, aliphatic polyolefins (e.g., polyethylene and polypropylene), and cyclic olefin copolymers. Among them, polyimide, liquid crystal polymer, syndiotactic polystyrene or cyclic olefin copolymer are preferred, with polyimide being even better.

[0114] One type of adhesive resin can be used alone, or two or more types can be used. The content of adhesive resin relative to the total mass of the adhesive layer is preferably 60~99.9% by mass, more preferably 70~99.0% by mass, and further preferably 80~97.0% by mass.

[0115] (Reactive compounds) The next layer may contain reactants of compounds having reactive groups, preferably reactive compounds. In this specification, compounds having reactive groups and their reactants are collectively referred to as "reactive compounds". It is preferable that the reactive groups of the reactive compound are groups that can exist on the surface of the polymer film (especially groups with oxygen atoms such as carboxyl and hydroxyl groups) and reactive groups. Examples of reactive groups include epoxy, oxetyl, isocyanate, anhydride, carbodiimide, N-hydroxy ester, glyoxal, acetoimide, halogenated alkyl, and thiol groups. Groups selected from at least one group derived from the group consisting of epoxy, anhydride, and carbodiimide are preferred, with epoxy being more preferred.

[0116] Specific examples of reactive compounds with epoxy groups include aromatic glycidylamine compounds (e.g., N,N-diepoxypropyl-4-epoxypropyloxyaniline, 4,4'-methylenebis(N,N-diepoxypropylaniline), N,N-diepoxypropyl-o-toluidine, and N,N,N',N'-tetraepoxypropyl-m-phenylenediamine, 4-tert-butylphenylepoxypropyl ether), aliphatic glycidylamine compounds (e.g., 1,3-bis(diepoxypropylaminomethyl)cyclohexane), and aliphatic glycidyl ether compounds (e.g., sorbitol polyepoxypropyl ether).

[0117] Specific examples of reactive compounds having an anhydride group include tetracarboxylic dianhydrides (e.g., 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, oxydiphthalic anhydride, diphenyl 3,4,3',4'-tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)sulfide dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl) Propane dianhydride, p-phenylenediamine bis(triphenylamine monoester anhydride), p-biphenylenediamine bis(triphenylamine monoester anhydride), meta-triphenyl-3,4,3',4'-tetracarboxylic acid dianhydride, p-triphenyl-3,4,3',4'-tetracarboxylic acid dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)phthalic anhydride, 1,4-bis(3,4-dicarboxyphenoxy)phthalic anhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, and 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid dianhydride).

[0118] Specific examples of reactive compounds having a carbodiimide group include monocarbodiimide compounds (e.g., dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, tributylisopropylcarbodiimide, diphenylcarbodiimide, di-tributylcarbodiimide, di-β-naphthylcarbodiimide, and N,N'-di-2,6-diisopropylphenylcarbodiimide) and polycarbodiimide compounds (e.g., as described in U.S. Patent No. 2,941,956, Japanese Patent Publication No. 47-033279, J. Org. Chem. Vol. 28, pp. 2069-2075 (1963), and Chemical Review). Compounds manufactured by the methods described in Volume 81, No. 4, pp. 619-621, etc. (1981). Commercially available reactive compounds containing carbodiimide groups include Carbodilite (registered trademark) HMV-8CA, LA-1 and V-03 (all manufactured by Nisshinbo Chemical Inc.), Stabaxol (registered trademark) P, P100 and P400 (all manufactured by Lanxess AG), and stabilizer 9000 (product name, manufactured by Raschig Chemie).

[0119] The reactive compound should have one or more reactive groups, but from the viewpoint of better adhesion between the polymer film and the metal-containing layer, three or more are preferred. There is no particular upper limit, for example, six or less, with five or less being preferred. As a reactant of a compound having a reactive group, it is not particularly limited as long as it comes from a compound having a reactive group. For example, a reactant obtained by reacting the reactive group of a compound having a reactive group with a group containing oxygen atoms present on the surface of a polymer film can be cited.

[0120] A single reactive compound may be used alone, or two or more may be used. The content of reactive compounds relative to the total mass of the adhesive layer is preferably 0.1 to 40% by mass, more preferably 1 to 30% by mass, and further preferably 3 to 20% by mass.

[0121] The next layer may further contain components other than adhesive resins and reactive compounds (hereinafter also referred to as "additives"). Examples of additives include inorganic fillers, hardening catalysts, and flame retardants. The additive content relative to the total mass of the adhesive layer is preferably 0.1 to 40% by mass, more preferably 1 to 30% by mass, and further preferably 3 to 20% by mass.

[0122] (thickness) When the laminate has an adhesive layer, from the viewpoint of better adhesion between the polymer film and the metal-containing layer, a thickness of 0.05 μm or more for the adhesive layer is preferred, 0.1 μm or more is even better, and 0.2 μm or more is further preferred. There is no particular upper limit, but 1 μm or less is preferred, 0.8 μm or less is even better, and 0.6 μm or less is further preferred. Furthermore, considering the superior adhesion between the polymer film and the metal layer, a ratio of 0.1% to 2% of the thickness of the adhesive layer to the thickness of the polymer film is preferred, and 0.2% to 1.6% is even better. Furthermore, the thickness of the aforementioned adhesive layer refers to the thickness of each adhesive layer. The thickness of the next layer can be measured using the method described above for measuring the thickness of polymer films.

[0123] [Manufacturing method of laminated bodies] The manufacturing method of the laminate is not particularly limited. For example, a method having the following process (hereinafter also referred to as "process B") can be cited: after laminating the polymer film and metal foil of the present invention, the polymer film and metal foil are pressed together under high temperature conditions, thereby manufacturing the laminate.

[0124] Process B In process B, the polymer film of the present invention and a metal foil composed of a metal constituting a metal layer are laminated together, and the polymer film and the metal foil are pressed together under high temperature conditions, thereby producing a laminate having a polymer film and a metal layer. The polymer film and metal foil used in process B are as described above. The method and conditions for hot-pressing the polymer film and metal foil in process B are not particularly limited, and can be appropriately selected from known methods and conditions. For the temperature conditions of hot pressing, the melting point of the polymer film is set as Tm (°C), with {Tm-80}°C to {Tm+30}°C being preferred, and {Tm-40}°C to Tm°C being even more preferred. For the pressure conditions of hot pressing, 0.1 to 20 MPa is preferred. The pressing time is preferably 0.001 to 1.5 hours.

[0125] The metal layer in the laminate can be a patterned metal wiring. The method for fabricating the metal wiring is not particularly limited. For example, a method can be used to form the aforementioned metal wiring by etching the metal layer after performing process B, which involves hot-pressing a polymer film and a metal foil. Alternatively, patterned metal wiring can be directly formed on the surface of the polymer film using known methods such as sputtering, ion plating, vacuum evaporation, and wet plating.

[0126] <Adhesive Layer Formation Process> In manufacturing a laminate having a polymer film, an adhesive layer, and a metal layer in sequence, a process is performed to form an adhesive layer on at least one side of the polymer film using an adhesive composition. Then, process B is performed using the obtained polymer film with the adhesive layer and a metal foil to obtain a laminate having the aforementioned adhesive layer.

[0127] As an adhesive layer formation process, an example is the process of coating an adhesive composition onto at least one surface of a polymer film and drying and / or curing the coating film as needed to form an adhesive layer on the polymer film.

[0128] Adhesive compositions may include, for example, compositions comprising the adhesive resin, reactive compounds, and additives described above, which are components constituting the adhesive layer, and solvents. Regarding the components constituting the adhesive layer, as stated above, their description is omitted.

[0129] Examples of solvents (organic solvents) include ester compounds (e.g., ethyl acetate, n-butyl acetate, and isobutyl acetate), ether compounds (e.g., ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl celusone acetate, ethyl celusone acetate, diethylene glycol monomethyl ether, and diethylene glycol monoethyl ether), ketone compounds (e.g., methyl ethyl ketone, cyclohexanone, cyclopentanone, 2-heptanone, and 3-heptanone), hydrocarbon compounds (hexane, cyclohexane, and methylcyclohexane), and aromatic hydrocarbon compounds (e.g., toluene and xylene).

[0130] One solvent can be used alone, or two or more solvents can be used. The solvent content is preferably 0.0005 to 0.02% by mass relative to the total mass of the adhesive composition, and more preferably 0.001 to 0.01% by mass. The content of solid components in the adhesive composition relative to the total mass of the adhesive composition is preferably 99.98~99.9995% by mass, and even more preferably 99.99~99.999% by mass. In this specification, the term "solid component" refers to the component obtained by removing the solvent (organic solvent) and water. That is, the solid component of the adhesive composition refers to the components that constitute the adhesive layer, such as the adhesive resin, reactive compounds, and additives mentioned above.

[0131] Methods for attaching adhesive components onto polymer films are not particularly limited, and examples include rod coating, spray coating, doctor blade coating, flow coating, spin coating, dip coating, mold coating, inkjet coating, and curtain coating. When drying the adhesive composition attached to the polymer film, there are no particular restrictions on the drying conditions, but a drying temperature of 25~200℃ and a drying time of 1 second~120 minutes are preferred. In the manufacturing method of the laminate, after performing the process of forming an adhesive layer using an adhesive composition, the laminate of the present invention can be manufactured by performing the above-described process B of laminating a polymer film and a metal-containing layer (and an adhesive layer) and hot-pressing the polymer film and the metal foil.

[0132] Furthermore, the method for manufacturing the laminate of the present invention having a polymer film and a metal layer is not limited to the method described above. For example, after coating the above-mentioned adhesive composition on at least one surface of a metal foil and drying and / or hardening the coating film as needed to form an adhesive layer, the metal foil with the adhesive layer and the polymer film are laminated together to form an adhesive layer in contact with the polymer film. Then, the metal foil, the adhesive layer and the polymer film are hot-pressed together according to the method described in process B, thereby manufacturing a laminate containing a polymer film, an adhesive layer and a metal layer in sequence. Alternatively, a metal-containing layer can be formed on the surface of a polymer film to create a laminate by using known methods such as vapor deposition, electroless electroplating, and electroplating.

[0133] The multilayer material manufactured by the above manufacturing method can be used in the manufacture of the above-mentioned multilayer circuit boards. For example, for the metal layer of the multilayer body (first multilayer body) manufactured by the above manufacturing method, a patterning process is performed to form metal wiring as needed. Then, the surface of the first multilayer body with metal wiring and the surface of the insulating layer of the second multilayer body formed by attaching a metal layer to one surface of an insulating layer made of a polymer film can be brought into contact with the surface of the first multilayer body on the metal wiring side and the surface of the second multilayer body on the insulating layer side. The multilayer body obtained by hot pressing according to the above process B is used to manufacture a multilayer circuit board. At this time, by using the polymer film of the present invention in the manufacture of the first laminate, it is possible to suppress the in-plane displacement (direction perpendicular to the lamination direction) of the metal wiring when laminating the first laminate and the second laminate.

[0134] [Applications of laminates] Applications of multilayer materials include multilayer circuit boards, flexible multilayer boards, and wiring boards for flexible printed circuit boards (FPCs). Multilayer materials are particularly preferred for use as substrates in high-speed communications. [Example]

[0135] The following examples provide a further detailed description of the present invention. The materials, amounts, proportions, processing contents, and processing steps shown in the following examples can be appropriately modified without departing from the spirit of the present invention. Therefore, the present invention is not limited to the forms shown in the following examples. Furthermore, unless otherwise specified, "parts" and "%" are based on mass.

[0136] [raw materials] <Liquid Crystal Polymer> Polymer films are manufactured using the liquid crystal polymer described below. • LCP1: Polyplastics Co., Ltd.'s "VECTRA (registered trademark) A950", thermoplastic liquid crystal polyester resin, melting point Tm: 280℃. • LCP2: Made by Polyplastics Co., Ltd., “VECTRA (registered trademark) C950”, thermoplastic liquid crystal polyester resin, melting point Tm: 320℃. Both LCP1 and LCP2 mentioned above are type II liquid crystal polymers composed of repeating units from p-hydroxybenzoic acid and repeating units from 6-hydroxy-2-naphthoic acid.

[0137] <Metal Foil> The following metal foils are used in the manufacture of metal-clad laminates. • Copper foil 1: Rolled copper foil, 12μm thick, surface roughness Ra0.9μm. • Copper foil 2: Rolled copper foil, 18μm thick, surface roughness Ra0.9μm. Furthermore, the surface roughness Ra of the copper foil is calculated by measuring the arithmetic mean roughness Ra at 10 points on the surface of the copper foil using a surface roughness measuring instrument (manufactured by Mitutoyo Corporation, product name: SURFTEST SJ-201) according to JIS B0601 standard, and the average measured value is used.

[0138] [Example 1] A polymer film was manufactured using the manufacturing apparatus shown in Figure 1 by the method described below. Furthermore, the detailed conditions for blow molding will be described later.

[0139] [Film-making process based on blown bag forming (process A)] After the LCP1 particles are pre-dried by heating at 150°C for 6 hours, they are fed into the cylinder (60 mm in diameter) of a single-shaft extruder and heated and mixed at 295°C. The molten LCP1 is then extruded from a ring die with the following structure at a die shearing speed of 1000 sec-1 to form a cylindrical film.

[0140] Then, using a manufacturing apparatus (blow-blow molding apparatus) with the following configuration, the extruded molten cylindrical film is cooled to its outer surface while air is supplied to the internal space, and it is expanded by internal pressure. At this time, the ratio of the elongation ratio in the TD direction (circumferential direction) to the MD direction (long side direction) of the expanded cylindrical film is 3. Furthermore, a specific heat treatment is performed on the cylindrical film that extends while moving upwards: the cylindrical film is heated at a position where the elongation ratio in the TD direction exceeds 90% of the final ratio, followed by cooling. More specifically, as a specific heat treatment, the cylindrical film is heated for 2 seconds using an infrared heater positioned at the aforementioned location to bring its surface temperature to the temperature described later. Immediately afterwards, it is cooled for 2 seconds using a cold air nozzle positioned directly above the infrared heater to reduce the surface temperature of the cylindrical film at the cooling rate described later. Next, it is trimmed and wound into a film shape.

[0141] Next, a easing treatment was performed: while applying tension to the film in the MD direction, it was introduced into a hot air drying oven set at 260°C for heating, thereby causing it to thermally shrink in the TD direction. The thermal shrinkage rate of the film before and after the easing treatment was 2%.

[0142] Next, the softened film was placed in a hot air drying oven set at 270°C and heated for 10 hours, thereby performing an annealing treatment that increases the molecular weight of the liquid crystal domains present inside the film. The annealed film is guided and conveyed by rollers, and the polymer film of the present invention is obtained by traction by clamping rollers. The thickness of the manufactured polymer film is 50 μm.

[0143] The manufacturing conditions and the configuration of the blow molding apparatus for the polymer film of Example 1 are shown below. • Extruder melt temperature: 295℃ • Raw material resin discharge temperature: 283℃ • Raw material resin (molten) discharge rate: 13 kg / hour • Diameter of the ring mold: 50mm • Slit width of the annular mold: 250μm • Location of the cooling ring: 30mm vertically above the annular mold • Temperature of the gas blown out from the cooling ring: 150℃ • Air velocity of the gas blown out from the cooling ring: 5 m / s • Location of the infrared heater: 350mm vertically above the annular mold • Thin film surface heating temperature: 290℃ • Location of the cooling device: 450mm vertically above the annular mold • Thin film surface cooling rate: -50℃ / second • TD directional expansion rate: 4 times • TD-direction expansion rate / MD-direction expansion rate: 3 • Traction speed of polymer film: 9.9 m / min

[0144] [Manufacturing of metal-coated laminates (Process B)] The polymer film manufactured in the above process and two copper foils 1 are continuously fed into the laminate between the heat-resistant rubber roller and the heated metal roller of the hot press and pressed together, thereby producing a copper-clad laminate formed by sequentially laminating copper foil 1, polymer film and copper foil 1. As the aforementioned heat-resistant rubber roller, a resin-coated metal roller (manufactured by Yuri Roll Machinery Co., Ltd., product name: Super-Tempex, resin thickness: 1.7cm) was used. Furthermore, a roller with a diameter of 40cm was used as both the heat-resistant rubber roller and the heated metal roller. The surface temperature of the heated metal roller is set to 260°C. In addition, the pressure applied to the polymer film and copper foil 1 between the heat-resistant rubber roller and the heated metal roller is set to 120 kg / cm² (converted to surface pressure).

[0145] [Examples 2 and 3] The annealing process was changed to the conditions described in Table 1 below. Otherwise, the polymer films of Examples 2 and 3 were manufactured according to the method described in Process A of Example 1. Next, in addition to using the polymer films that were manufactured, copper-clad laminates of Examples 2 and 3 were fabricated according to the method described in process B of Example 1.

[0146] [Example 4] Except for annealing by the method shown below, the polymer film of Example 4 was manufactured according to the method described in process A of Example 1. The annealing process in Example 4 was as follows. First, a composite with a softened film deposited on an adhesive (copper foil) was fabricated. Next, the resulting composite was hot-pressed at 300°C for 1 hour. Furthermore, the pressure applied to the composite was set to 40 kg / cm² (surface pressure conversion). Afterward, the cylindrical film was peeled off from the annealed adhesive to obtain the annealed film. Next, except for using the polymer film that was manufactured, the double-sided copper-clad laminate of Example 4 was produced according to the method described in Process B of Example 1.

[0147] [Example 5] The polymer film of Example 5 was manufactured in the same manner as described in process A of Example 1. Next, using the polymer film manufactured and replacing the two copper foils 1 with two copper foils 2 as described above, the double-sided copper-clad laminate of Example 5 was produced according to the method described in process B of Example 1.

[0148] [Example 6] The polymer film of Example 6 was manufactured in the same manner as described in process A of Example 1. Next, before performing process B, a crosslinking agent solution (crosslinking agent: N,N-diepoxypropyl-4-epoxypropyloxyaniline (manufactured by Sigma-Aldrich Co. LLC), solvent: toluene, crosslinking agent concentration: 10% by mass) was coated on both sides of the polymer film as an adhesive. The solvent components were removed by drying in a continuous drying oven at 110°C, thereby obtaining a polymer film with adhesive layers on both sides. The thickness of the dried adhesive layer was 0.001 mm. In addition to using a polymer film formed by applying an adhesive layer to both sides, the copper-clad laminate of Example 6 was manufactured according to the method described in process B of Example 1.

[0149] [Example 7] The polymer film of Example 7 was manufactured in the same manner as described in process A of Example 3. Next, except that the polymer film was used, the double-sided copper-clad laminate of Example 7 was fabricated in the same manner as in Example 6.

[0150] [Example 8] The polymer film of Example 8 was manufactured in the same manner as described in process A of Example 4. Next, except that the polymer film was used, the double-sided copper-clad laminate of Example 8 was fabricated in the same manner as in Example 6.

[0151] [Example 9] The polymer film of Example 9 was manufactured by using LCP2 instead of LCP1 as the raw material for the liquid crystal polymer, changing the heating temperature in the specific heat treatment to the conditions described in Table 1 below, and changing the annealing treatment to the conditions described in Table 1 below. Next, using the manufactured polymer film and setting the surface temperature of the heated metal roller to 290°C, the double-sided copper-clad laminate of Example 9 was fabricated according to the method described in Process B of Example 1.

[0152] [Comparative Example 1] The polymer film of Comparative Example 1 was manufactured according to the method described in process A of Example 1, except that no specific heat treatment or annealing treatment was performed on the film formed by blow molding. Next, using the polymer film manufactured and replacing the two copper foils 1 with two copper foils 2 as described above, a double-sided copper-clad laminate of Comparative Example 1 was produced according to the method described in process B of Example 1.

[0153] [Comparative Example 2] Except for not subjecting the film formed by blow molding to specific heat treatment, the polymer film of Comparative Example 2 was manufactured according to the method described in Process A of Example 1. Next, using the polymer film manufactured and replacing the two copper foils 1 with two copper foils 2 as described above, a double-sided copper-clad laminate of Comparative Example 2 was produced according to the method described in process B of Example 1.

[0154] [Properties of Polymer Films] <Void Area Ratio> The porosity ratio of the polymer films manufactured in each example was measured using the following method. At room temperature (25°C), the polymer films manufactured in each example were cut along the thickness direction using a diamond slicing tool. The exposed sections of the polymer film were then immersed in methylamine for 4 hours at room temperature (25°C). Distilled water was added to the sections for cleaning, and the water droplets were removed using an air dust collector. Subsequently, the cross-sections of the polymer films were imaged using a scanning electron microscope (SEM) (Hitachi High-Tech Fielding Corporation, "S-4800 type") at an accelerating voltage of 2kV and a magnification of 3000x. The captured image was binarized using the Threshold function of the image processing software "ImageJ," separating the image into dark and bright areas to obtain image processing data. The image processing software automatically determined the critical value for binarization based on the contrast of the captured image, which was between 88 and 105 out of 256 levels. The captured image ranged from 15 μm in the thickness direction to 42 μm in the transport direction. The dark areas in the binarized image processing data correspond to the void regions of the polymer film. Based on the binarized image processing data, the area of ​​the dark area is automatically detected and measured. The area of ​​each gap region is calculated from the obtained measurement values, and the average area of ​​the gap region is also calculated. Starting from one surface of the polymer film and moving towards another, position T1 is defined as the distance at 1 / 10 of the polymer film thickness, position T2 as the distance at 4 / 10 of the polymer film thickness, and position T3 as the distance at 6 / 10 of the polymer film thickness. The region from one surface to position T1 is defined as the first surface region, and the region from position T2 to position T3 is defined as the central region. Binarized data is obtained from images with n=2, and the void area ratio X, which represents the area of ​​voids in the first surface region, and the void area ratio Y, which represents the area of ​​voids in the central region, are calculated. Each void area ratio refers to the ratio (%) of the area of ​​voids in each region to the area of ​​each region of the polymer film cross-section. Table 1, described later, shows the value of "void area ratio Y - void area ratio X" (denoted as (YX) in the table).

[0155] <Hardness> The hardness of the polymer films manufactured in each example was measured by the following method. The polymer films manufactured in each example were embedded in epoxy resin. The embedded polymer film was then cut along its thickness direction, and the exposed cross-section was ground using a slicing machine to obtain a measuring section. In the obtained section, the hardness A at position A, located at a distance of half the thickness of the polymer film from one surface to another, and the hardness B at position B, located at a distance of 1 / 10 the thickness of the polymer film from one surface to another, were measured using nanoindentation. Measurements were performed according to ISO 14577. Specifically, measurements were taken at six points at each location using a TI-950 (nano-friction indenter) (manufactured by Bruker Japan KK) with a Berkovich indenter and an indentation load of 500 μN. The arithmetic mean of the six points was taken as the hardness (unit: GPa). Table 1, described later, shows the values ​​of "(hardness A + hardness B) / 2" (referred to as (A + B) / 2 in the table) and "hardness A - hardness B" (referred to as (AB) in the table).

[0156] <Dielectric Properties> Samples were cut along the overall thickness direction of the polymer films manufactured in each example, and the dielectric loss tangent in the 28 GHz frequency band was measured using a split-cylinder resonator (KANTO Electronic Application and Development Inc. "CR-728") and a network analyzer (Keysight N5230A) at an environment of 23°C and 65% RH. The measured dielectric loss tangent values ​​were evaluated using the following criteria. A: The dielectric loss tangent is below 0.0021. B: Dielectric loss tangent is greater than 0.0021 and less than 0.0024. C: Dielectric loss tangent exceeds 0.0024

[0157] <Thermal Properties> The coefficient of linear expansion of the polymer films manufactured in each example was measured by the following method. Samples measuring 6 mm in width and 6 mm in length were cut from the center of the polymer films manufactured in each example. The samples were placed on the stage of a thermomechanical analysis apparatus (TA Instruments Japan Inc. "TMA-Q400"), and the in-plane coefficient of linear expansion (CTE) of the polymer films was measured. The measured CTE values ​​were evaluated according to the following criteria. Furthermore, the CTE of copper is 18 ppm / ℃. A: The coefficient of linear expansion is 17~19 ppm / ℃ B: Linear expansion coefficient exceeding 19 ppm / ℃ but below 23 ppm / ℃, or above 13 ppm / ℃ but less than 17 ppm / ℃ C: Linear expansion coefficient exceeding 23 ppm / ℃ or less than 13 ppm / ℃

[0158] [result] Table 1 below shows the manufacturing conditions and characteristics of the polymer film, the manufacturing conditions of the metal-coated laminate, and the evaluation results for each embodiment and comparative example. The “Resin” column in Table 1 shows the type and melting point (unit: °C) of the resin (liquid crystal polymer) used in the manufacture of polymer films in each example. The “Manufacturing of Polymer Films” column in Table 1 shows the specific heat treatment and annealing methods and conditions in process A.

[0159] [Table 1] resin Manufacturing of polymer films Manufacturing of metal-coated laminates Polymer film properties type Melting point (°C) Manufacturing conditions heating (°C) cool down (℃ / second) annealing copper foil Next layer fit (Two sides) thickness Void area ratio hardness Dielectric properties thermal properties condition (YX) (A+B) / 2 (AB) Dielectric loss tangent coefficient of linear expansion μm % GPa GPa evaluate value evaluate Value (ppm / ℃) Example 1 LCP1 280 Heating + Cooling 290 -50 270℃×10 hours Copper foil 1 none Hot pressing 260℃ 50 0.10 0.17 0.010 A 0.0021 A 17 Example 2 LCP1 280 Heating + Cooling 290 -50 300℃ × 10 seconds Copper foil 1 none Hot pressing 260℃ 50 0.50 0.15 0.020 B 0.0024 B twenty two Example 3 LCP1 280 Heating + Cooling 290 -50 300℃×1 hour Copper foil 1 none Hot pressing 260℃ 50 0.20 0.16 0.020 B 0.0022 A 18 Example 4 LCP1 280 Heating + Cooling 290 -50 300℃×1 hour (with stamping) Copper foil 1 none Hot pressing 260℃ 50 0.30 0.15 0.010 B 0.0023 B 20 Example 5 LCP1 280 Heating + Cooling 290 -50 270℃×10 hours Copper foil 2 none Hot pressing 260℃ 50 0.10 0.17 0.010 A 0.0021 A 17 Example 6 LCP1 280 Heating + Cooling 290 -50 270℃×10 hours Copper foil 1 have Hot pressing 260℃ 50 0.10 0.17 0.010 B 0.0022 A 17 Example 7 LCP1 280 Heating + Cooling 290 -50 300℃×1 hour Copper foil 1 have Hot pressing 260℃ 50 0.20 0.16 0.020 B 0.0023 A 18 Example 8 LCP1 280 Heating + Cooling 290 -50 300℃×1 hour (with stamping) Copper foil 1 have Hot pressing 260℃ 50 0.30 0.15 0.010 B 0.0024 B 20 Example 9 LCP2 320 Heating + Cooling 330 -50 300℃ × 10 seconds Copper foil 1 none Hot pressing 290℃ 50 0.40 0.16 0.020 B 0.0024 A 18 Comparative Example 1 LCP1 280 - - - - Copper foil 2 none Hot pressing 260℃ 50 0.00 0.08 0.005 C 0.0025 C 28 Comparative Example 2 LCP1 280 - - - 270℃×1 hour Copper foil 2 none Hot pressing 260℃ 50 0.05 0.14 0.005 B 0.0024 C twenty four

[0160] The results shown in the table above confirm that the polymer film according to the present invention can solve the problems of the present invention.

[0161] 10: Film forming device 12: Ring mold 14: Cooling blower 16: Heater 18: Cooler

Claims

1. A polymer film comprising a liquid crystal polymer, wherein, in a cross-section cut along the thickness direction of the polymer film, when the hardness at position A, located at a distance of half the thickness of the polymer film from one surface toward another, is defined as hardness A, and the hardness at position B, located at a distance of 1 / 10 the thickness of the polymer film from one surface toward the other, is defined as hardness B, the following relationship (1A) is satisfied. In the aforementioned cross-section, when moving from one surface of the aforementioned polymer film towards the other surface, with position T1 defined as a distance of 1 / 10 of the thickness of the aforementioned polymer film, position T2 defined as a distance of 4 / 10 of the thickness of the aforementioned polymer film, and position T3 defined as a distance of 6 / 10 of the thickness of the aforementioned polymer film, the region from the aforementioned surface to position T1 is defined as the first surface region, and the region from position T2 to position T3 is defined as the central region, the area ratio of voids in the aforementioned first surface region is defined as the void area ratio X, and the area ratio of voids in the aforementioned central region is defined as the void area ratio Y, the following relationship (2A) is satisfied: Equation (1A) (hardness A + hardness B) / 2 ≥ 0.10 GPa Equation (2A) Void area ratio Y - void area ratio X ≥ 0.10%, wherein the aforementioned liquid crystal polymer comprises at least one unit selected from the group consisting of repeating units from p-hydroxybenzoic acid and repeating units from 6-hydroxy-2-naphthoic acid. The polymer film therein has a single-layer structure.

2. The polymer film as claimed in claim 1, wherein the aforementioned hardness A and the aforementioned hardness B satisfy the following relationship (1B): Equation (1B) (hardness A - hardness B) ≥ -0.02 GPa.

3. The polymer film as claimed in claim 1 or claim 2, wherein the dielectric loss tangent of the aforementioned polymer film at a temperature of 23°C and a frequency of 28GHz is less than 0.0024.

4. A laminate having a polymer film as described in any one of claims 1 to 3, and at least one metal-containing layer.

5. The laminate as described in claim 4, having at least two aforementioned metal-containing layers, wherein the aforementioned metal-containing layers, the aforementioned polymer film, and the aforementioned metal-containing layers are sequentially disposed.

6. The laminate as described in claim 4, wherein the thickness of the aforementioned metal layer is 5 to 30 μm.

Images